Electric motor and compressor construction

ABSTRACT

An electric motor-gas pump unit mounted in a hermetic sealed housing with the end turns of the motor stator windings each arranged in a horseshoe configuration to define two axially aligned winding gaps which register with an unslotted portion of the laminated stator core so that the same can serve as a mounting platform for the pump. The stator core thus serves its usual function as a support for the windings and as a flux conductor, and in addition serves as a supporting frame for the pump unit. One or two bearing arms are also cantilever mounted on the unslotted portion of the stator core to serve as the journal for the rotor shaft-crankshaft of the motor-pump unit.

United States Patent Inventor Theodore W. Rundell Tecumseh, Mich.

Appl. No. 20,994

Filed Mar. 19, 1970 Patented Oct. 5, 1971 Assignee Tecumseh ProductsCompany Tecumseh, Mich.

ELECTRIC MOTOR AND COMPRESSOR CONSTRUCTION 26 Claims, 16 Drawing Figs.

U.S. CI 417/415, 7 310/254, 417/902 Int. Cl ..F04b 35/04, H02k l/12Field of Search 417/415, 902, 410; 310/254 7 [56] References CitedUNITED STATES PATENTS 2,905,372 9/1959 LaFlame 417/415 X 3,407 ,990 10/1968 Schaefer 417/902 Primary Examiner-Robert M. Walker Attorney-Barnes,Kisselle, Raisch & Choate ABSTRACT: An electric motor-gas pump unitmounted in a hermetic sealed housing with the end turns of the motorstator windings each arranged in a horseshoe configuration to define twoaxially aligned winding gaps which register with an unslotted portion ofthe laminated stator core so that the same can serve as a mountingplatform for the pump. The stator core thus serves its usual function asa support for the windings and as a flux conductor, and in additionserves as a supporting frame for the pump unit. One or two bearing armsare also cantilever mounted on the unslotted portion of the stator coreto serve as the journal for the rotor shaftcrankshaft of the motor-pumpunit.

PATENTEU um 512m 7.916 10.784

sum 1 0F 5 INVENTOR 2 THEODORE w. RUNDELL ATTORNEYS PATENTEDUEI 5:971

SHYU 2 OF 5 INVENTOR THEODORE W. RUNDELL FIGS ATTORNEYS PATENTEDHEI51971 3,610,784

SHEET 3 [IF 5 M Mi FIG. 9

H-IVENTOR THEODORE RUNDELL ATTORNFY PATENTEUUBI 519m 3.610.784

SHEET U UF 5 Q INVENTOR THEODORE W. RUNDELL ATTORNEYS ELECTRIC MOTOR ANDCOMPRESSOR CONSTRUCTION This invention relates to electric motors andmotor driven piston pumps, and more particularly to improvements in theconstruction of motor compressor units for hermetic compressors used inrefrigeration systems, air conditioning and similar applications.

An object of the present invention is to provide an electric motorhaving field windings arranged in a manner such that a pump or otherdevice to be driven by the motor may be mounted directly on the statorof the motor to thereby provide a compact and economical integrated pumpand motor unit.

Another object is to provide an improved heremetic compressorincorporating an electric motor and compressor pump unit of the abovecharacter to hereby achieve a reduction in the axial dimension of thecompressor casing as well as substantial savings in the cost and weightof the heremetic compressor assembly.

Other objects, features and advantages of the present invention willbecome apparent from the following detailed description taken inconjunction with the accompanying drawings wherein:

FIG. 1 is a vertical sectional view taken on the line II of FIG. 2illustrating a hermetic compressor incorporating one embodiment of anelectric motor and pump construction of the present invention.

FIG. 2 is a horizontal sectional and top plan view taken on the lineII-II of FIG; 1 but on a reduced scale.

FIG. 3 is a fragmentary vertical sectional view taken on the lineIII-III of FIG. 2 but enlarged thereover and illustrating structure bywhich the motor-compressor unit is mounted to the casing.

FIG. 4 is horizontal sectional and bottom plan view taken on the lineIV-IV of FIG. 1 on the same scale as FIG. 2.

FIG. 5 is a vertical section and end elevational view taken on the lineV-V of FIG. 1 and drawn to the scale of FIG. 1, and with a portionbroken away to better illustrate the mounting stud construction.

FIG. 6 is a top plan view of the stator core of the electric motor shownby itself and on a reduced scale.

FIGS. 7, 8, 9 and 10 are perspective views of one embodiment of a statorused in the electric motor of the invention showing various stages ofthe installation of the run and start windings on the stator core inaccordance with the present invention.

FIG. 1 l is a fragmentary vertical sectional similar to that of FIG. Iillustrating a second embodiment of an electric motor and pumpconstruction in a hermetic compressor of the present invention.

FIGS. 12 and 13 are bottom plan and end elevational views respectivelyof a modified cylinder block and bearing support unit ofthe pump ofFlG.I1.

FIGS. 14 and 15 are top and bottom plan views respectively of the mainjournal of the pump of FIG. 11.

FIG. 16 is a vertical sectional view taken on the line XVI- XVI of FIG.14.

Referring in more detail to the accompanying drawings, FIG. 1illustrates a hermetic compressor assembly 20 comprising a three-parthermetically sealed casing made up of a cylindrical center section 22and top and bottom caps 24 and 26 respectively attached by welded sealedjoints to section 22. A conventional glass terminal unit 28 is providedin top 24 for connection to the internal and external electrical leads(not shown) for energizing the electric motor 32 of the motor-compressorunit 30 which is mounted inside the casing. Motorcompressor unit 30preferably includes an induction-type electric motor illustrated by wayof example herein as a splitphase induction motor 32 with a distributedwinding type stator and cast rotor and adapted to operate on singlephase 60- cycle l 10 volt nominal alternating current, and a singlecylinder reciprocating piston gas pump 34 mounted directly on the motorin accordance with a principal feature of the present invention.

Motor 32 comprises a laminated stator core 36 of annular configuration(FIG. 6) made up of a plurality of laminations made of the usualferromagnetic material normally employed in electric motor stator coreconstruction. Each stator core lamination is preferably individuallybonded to the adjacent lamina by a layer of adhesive preferably an epoxytype adhesive, which prevents lateral slippage of the lamina and impartsa high degree of strength to the stator lamination so that it can alsoserve as a frame for supporting pump 34 and other components of unit 30.As best seenin FIG. 6, the stator core 36 illustrated herein by way ofexample has concentric cylindrical inner and outer peripheries 38 and 40respectively with a circular row of winding slots 42-60, hereinillustrated by way of example as 20 in number, which extend axiallythrough the stator and are open at their upper and lower ends. Each slotis of generally oval cross section and extends radially outwardly froman associated winding insertion slot 42', 44, etc. in the innerperiphery 38 of the stator, the radially outer ends of slots 42-80 beingdisposed about midway between the inner and outer peripheries of thestator.

As will be noted from FIGS. 6-10 inclusive, core 36 has an unslottedportion 82 extending approximately 60 circumferentially between the endslots 42 and (see FIG. 6). The unslotted portion 82 of the stator isthus imperforate except for two bolt holes 84 and 86 extending axiallytherethrough, and thus has axially opposite exposed flat top and bottomsurfaces adapted to serve as mounting platforms for the cylinder block136 of pump 34 and the outboard bearing bracket 150 respectively, asdescribed in more detail hereinafter. In cooperation with thisinterrupted core slot arrangement the distributed run and start windingsmotor 32 are asymmetrically arranged as best seen in FIGS. 7-10inclusive to further accommodate the mounting of the pump directly onthestator.

Referring first to FIG. 7, core 36 is shown with two sets of runwindings (electrically interconnected as one winding) partiallyinstalled on the stator. The distributed run winding which forms theright hand pole of the stator field (as viewed in FIGS. 7 and 8)consists of four coils 90, 92, 94 and 96 having upper and lower endturns which extend beyond the axially opposite top and bottom endsurfaces of core 36. The upper end turns of these coils are shown laiddown in superimposed relation on the right-hand upper end surface of thestator as viewed in FIG. 7. Coil 96 is wound so that one run extendsthrough stator slot 56 and the other run through stator slot 66, and theupper end turn portion of coil 96 extends circumferentially and liesagainst the upper most lamination of stator 36. Similarly, coil 94 iswound through slots 54 and 68, coil 92 through slots 52 and 70, and coilthrough slots 50 and 72, and the upper end turns of coils 94, 92 and 90also extend circumferentially above the stator in successive superposedrelation to the upper end turn of coil 96. Coils 90-96 thus form adistributed winding arrangement for generating a right-handelectromagnetic field pole centered between slots 60 and 62 on animaginary diametrical line 120 (FIG. 6).

The left-hand field pole as viewed in FIGS. 7 and 8 is also formed by adistributed array of four run winding coils 98, I00, I02 and 104. Coil98 is wound through slots 48 and 74, coil 100 through slots 46 and 76,coil 102 through slots 44 and 78 and coil 104 through slots 42 and 80.The upper end turns of coils 98-104 are shown loosely separated in FIG.7 to better illustrate the progressive increase in the length of each ofthese coils. The upper end turns of coils 98, 100, 102 and 104 arelonger than the end turns of coils 90-96 so that they are of sufiicientlength to be laid down upon one another over the upper end turns ofcoils 90-96 is shown in FIG. 8. Hence the upper end turns of all eightcoils 90-104 in their final assembled position extend circumferentiallyin succesive superimposed relationship from their respective statorslots around the right end of core 36 as shown in somewhat exaggerateddiagrammatic form in FIG. 8. g

It is to be understood that the lower end turns of each of the coils90-104 are likewise disposed in a similar successive superposed-arraybeneath and adjacent the bottom end surface of core 36. The final foldedassembly of all run and start winding lower end turns in shown in FIGS.7-10 inclusive as an indistinguishable mass of windings 106 which areheld together with suitable binding cords 108 as in conventional motorwinding construction practice. It is also to be understood that theupper end turns of the run and start windings are likewise arranged andsecured as indicated at 132 in FIGS. 1,2 and 5. However, only the runwindings are shown in FIG. 7 and 8 and only the upper end turns of thestart windings are shown in FIGS. 9 and 10, the upper end turns beingshown somewhat exaggerated and separately identifiable in these views inorder to facilitate understanding.

Although the end turns of the left run winding coils 98-104 are pulledpack and down from their FIG. 7 position to their FIG. 8 position so asto overlie the right-hand side of core 36, the effective electricalcenter or pole of the field generated by these left-hand coils liesalong line 120 midway between bolt holes 84 and 86 so as to bisect themounting portion 82 of the stator. Hence the right and left field polesof the continuous run winding remain diametrically opposed to oneanother to confonn to split phase induction motor practice despite theasymmetrical arrangement of the individual coils of the main or runwinding.

The arrangement and distribution of the distributed coil auxiliary orstart winding is also altered from conventional split phase distributedwinding motor construction. Thus, referring to FIG. 9, the first half ofthe start winding consists of four progressively shorter coils 110, 112,114 and 116 arranged with their respective end turns projecting aboveand below (axially beyond) core 36. The smallest of these coils 116 iswound through slots 48 and 54, the next larger coil 114 is wound throughslots 46 and 56, coil 112 through slots 44 and 58 and coil 1 10 throughslots 42 and 60. The start winding coils 110-116 are disposed radiallyinwardly of those run winding coils which extend through the same slotsas described previously. In their final assembled position the end turnsof coils 110-116 are nested compactly against the inner periphery of thesurrounding run winding end turns and held thereagainst by binding cordssimilar to cords 108. For clarity, in FIG. 9 the upper end turns of thestart winding coils 110-116 are shown separated and exaggerated inlength, their final assembled position more nearly'resembling therelationship of these end turns as shown in FIG. 10. The lower end turnsof start windings 110-116 are arranged in a similar manner beneath core36.

As shown in FIG. 10, the electrical center or pole of the auxiliary orstart field generated by the distributed array of the coils 110-116 iscentered along a radial line 118 running midway between slots 50 and 52(FIGS. 6 and 10), or at an angle of about 75 from the diametrical line120 which represents the common axis of the left and right electricalpoles of the run winding.

Referring to FIG. 10, the second half of the start winding likewiseconsists of four coils I22, 124, 126 and 128 arranged in a distributedarray symmetrically about line 120 and opposite start winding coils110-116. Coil 122 is thus wound through slots 80 and 62, coil 124through slots 78 and 64, coil 126 through slots 76 and 66, and coil 128through slots 74 and 68. Thus, the electrical center or pole of theauxiliary field generated by start winding coils 122-128 lies along aline 130 likewise oriented about 75 from center line 120, but on theopposite side thereof from line 1 18.

Returning again to FIGS. 1-5 inclusive, it will now be better understoodthat the integrated mass of upper end turns of the start and runwindings are illustrated semischematically as an annular parted ring 132above core 36 (FIGS. 1 and 2), nd likewise the lower end turns of thestart and run windings are similarly shown as a parted annular ring 134beneath core 36 (FIGS. 1 and 4). As indicated above, the open portion 82of core 36, which is free or clear of any windings, supports a castaluminum cylinder block 136 which has a mounting boss 138 on itsunderside seating directly against the upper surface of portion 82 ofcore 36. Block 136 has cast integrally therewith an inboard bearingbracket 140, which includes a pair of downwardly sloping reinforcingribs 141 (FIG. 1), and which extends radially inwardly of the stator.The inner end of bracket has a rounded dependent bearing hub portion 143beveled on its underside. Hub 143 has a through-bore 142 orientedcoaxially with stator 36. The rotor shaft I44 of motor 32 has anenlarged upper end or hub 146 which is joumaled in bore 142 for rotationabout a vertical axis centrally of the stator. A conventional cast rotor148 for a split-phase induction motor is secured by a press fit to shaft144 for rotation therewith. It is to be noted that bracket 140 and boss138 are cut away on their undersides to form an arcuate notch 141 toprovide running clearance for the upper end turns 149 of rotor 148.

Shaft 144 is also supported in an outboard bearing bracket 150 having ahub portion 152 serving as the lower journal for shaft 144. Bracket 150is cantilever mounted at its left hand end 154 (as viewed in FIG. 1)against the underside of portion 82 of core 36 by a pair of mountingstuds 156 and 158 (FIG. 4) inserted respectively through associatedholes in bracket 150 and bolt holes 86 and 84 respectively. The upperends of studs 156 and 158 are threadably received in threaded blindbores 160 (FIG. 1) formed in the underside boss 138 of block 136, thusaligning and clamping block 136 and bracket 150 securely against theupper and lower surfaces of portion 82 of stator 36.

As shown in FIG. 5, preferably the head 158a and shank 158b of each ofthe studs 158 and 156 are electrically insulated from the adjacentsurfaces of bracket 154 and the laminations of core 36 by an insulatingwasher 157 and an insulating coating or tube 159 applied to shank 158b.This insulation serves to prevent flux-induced circulation of eddycurrents in what would otherwise be a closed electrical circuit made upof bolts 156 and 158, bracket 154 and boss 138.

The subassembly of shaft 144 and rotor 148 is vertically supported on athrust washer 162 disposed between the underside of the core 164 ofrotor 148 and the machined upper end surface 166 of hub 152. The drivingconnection between the motor shaft 144 and the piston 168 of pump 34 maybe any suitable crank mechanism, such as a scotch yoke, but as shownherein comprises a crankpin 172 mounted eccentrically on the upper endof the shaft hub 146, pin 172 being joumaled in the big end 174 of aconnecting rod 176. The small end 178 of rod 176 is spherical in shapeand received in a spherically shaped cavity 180 formed in piston 168 andswedged about its entrance after insertion of end 178 to provide a balland socket connection between rod 176 and piston 168. Piston 168reciprocates in a cast iron cylinder liner 182 mounted in block 136.

The valving and chambering of pump 34 generally follows a conventionalhermetic compressor practice and consists of a combined valve plategasket and intake valve leaf to form intake valve leaf plate 184, valveplate 186, combined discharge valve leaf and head gasket to fonndischarge valve plate 188, and head 190, all of which are clamped inassembled relation against block 136 by four head bolts 192 (FIGS. 1 and5). The working chamber 194 of pump 34 communicates with the intakemanifold chamber 196 (FIG. 1) via one intake port 202 (FIG. 5)controlled by the aforementioned intake valve of plate 184. Compressedrefrigerant gas is discharged from chamber 194 on the pumping stroke ofpiston 168 via three discharge ports 204, 206 and 208 (FIG. 5), past asemicircular leaf-type discharge valve 210, into a discharge manifoldchamber 212.

The gaseous refrigerant is conducted from the interior space of easing22-26 to chamber 196 via a suction tube and muffler assembly 214. Thisassembly consists of mufiler casing 216 having a pair of inlet tubes 218leading to the interior of casing 216, suitable muffling baffles withinthe casing and a pair of outlet tubes 220. These tubes are inserted intocorresponding bores 221 (shown in the manifold block of FIG. 13) in theupper portion of block 136 which in turn communicate with a chamber 221'formed in the block above cylinder liner 182. Chamber 221' communicateswith suction chamber 196 via two ports 198 and 200 shown in FIG. 5.

The pressurized refrigerant is conducted from discharge chamber 212 viaa suitable tubular discharge conduit (not shown) which extends withinthe interior space of casing 22 and through a sealed aperture in thewall of the casing to provide an exterior outlet connection in aconventional manner.

Preferably motor-compressor unit 30 is resiliently suspended withincasing 22 by a four-point spring suspension best seen in FIGS. 2, 3 and4. Thus, four right angle channel brackets 222 are arranged at 90intervals around the inner wall of casing 22 (FIG. 2) and spot weldedthereto as best seen in H0. 3. The uppermost lamination 224 of statorcore 36 is provided with four radially outwardly projecting care 226which extend beneath the horizontal leg 228 of the associated bracket222. Suitable slots are formed in each leg 228 and ear 226' forrespectively receiving the opposite end turns of a tension coil spring230, whereby the motor-compressor unit 30 is resiliently suspended bythe four springs 230 from the four brackets 222.

The bottom cap 26 of the hermetic casing is formed with a centraldepression 27 which forms a sump in which oil collects to providelubrication for the sealed hermetic compressor in accordance withconventional practice. Positive lubrication is provided by acentrifugal-type oil pump 232 which is mounted in the lower end of thehollow shaft 144 such that the inlet aperture 234 of pump 232 alwaysremains submerged in the pool of oil in the casing sump. When shaft 144is rotated by a motor 32, pump 232 forces oil upwardly within shaft 144,from which it is conducted via suitable oil passages (not shown) tolubricate the upper and lower shaft bearings 140 and 152. Further oilslinging passages and ports of known construction may be provided in theshaft 144 and/or hub 146 to lubricate the piston, connecting rod andassociated bearings.

In operation, motor 32 is energized via the conventional lead-inconnections and electrical control equipment, including suitablecapacitance or resistance start circuitry associated with the energizingcircuit for start winding ll1 16 and 1 12-128. Starting torque isdeveloped by the angular spacing of the auxiliary poles relative to themain poles and the electrical phase difference between the main andauxiliary winding currents. This torque is developed in rotor 148electromagnetically, thereby rotating shaft 144 which, through rod 176,imparts reciprocation to piston 168, thereby causing gaseous refrigerantto be withdrawn from the interior space of the casing and pumped by pump34 to the discharge outlet of the compressor, as will be well understoodby those skilled in the art from the foregoing description.

Despite the asymmetrical redistribution of the start and run windingsinto what may be termed a horseshoe configuration as viewed in FIGS. 2and 4, it has been found that sufficient starting as well as runningtorque is developed by motor 32 to satisfy commercial refrigerationrequirements. This has been achieved without any significant increase inpower input to the motor. Preferably cylinder block 136 and integralinboard bearing bracket 140 are constructed of cast aluminum orstructural aluminum alloys, or other suitable nonmagnetic material. Useof such nonmagnetic materials in the more massive parts adjacent core 36has been found to be critical in accomplishing an adequatestarting-torque versus crankshaftspeed curve. However, mounting bolts156 and 158 may be constructed of high-strength ferromagneticmaterial-such as steel if properly electrically insulated as describedpreviously. Also, in, order to provide wear resistance and long life,cylinder liner 82 is made of cast iron and piston 168 is constructed ofsteel or cast iron.

Successful results have been obtained using electric motors in the l/ 12to H6 horsepower range constructed in accordance with the drawings tooperate the compressor in a 300 to 500 B.t.u. per hour capacity range.These motors are generally of the asynchronous split-phase single-phaseinduction type designed to run at about 3,450 rpm. with a stator stackheight of about 1% to 1% inches within the parameters as set forth aboveand in the examples as specified hereinafter.

By way of further illustration, and not by way of limitation, twosuccessful motor-pump units 30 constructed in accordance with theinvention utilized the following design criteria:

EXAMPLE A M HP, 115-volt, 60-cycle, stack height 1% Start winding data:

Resistance 16.7 ohms. Wire size. No. 26 AWG (1 strand). Total length 400it. Poles Series.

Coils (as numbered 112 114 116 in FIG 10) 122 124 126 128 No. forwardturns 100 30 20 20 N 0. reverse tums 67 Total turns-.. 167 30 29 20 Mainwinding data:

Resistance 4.80 ohms.

N0. 23 AWG (2 parallel strands). 930 ft. es Series.

Coils (as numbered 111 FIG. 7) 104 102 100 98 90 92 96 N0. turns. 25 4854 60 60 54 48 25 Stator O.D. Stator I.D Rotor I.D 2.376 in. Pump data:

Bore 822 in Stroke .466 in. Displacement. .247 infi/revolution. Oilcharge 10 oz. Suction press. 4.5#/in.

(rating point). Head press. (rating ISM/m3 point). Pumping rate 320B.t.u./hr.

EXAMPLE B )6 HP, -volt, GO-cycle, stack height 1% Start winding data:

Resistance. 12.28 ohms. Wire size. N o. 25 AWG (1 strand). Total length400 ft.

es Series.

Coils (as numbered 110 112 114 116 in FIG. 10). 122 124 126 128 No.forward turns. 89 27 27 21 No. reverse turns. 26

Total turns.-. 151 27 27 21 Main winding data:

Resistance 3.1 ohms.

' 1%.{22 AWG (2 parallel strands).

t. Poles Series Coils (as numbered in F1 7) 104 102 100 98 90 92 [#4 .1638 43 48 48 43 38 g 17 .334 ind/revolution. Oil charge. 8 oz. Suctionpress. 4.5#/in.

(rating point). Head press. (rating #/in.

point). Pumping rate. 430 B.t.u./hr.

From the foregoing description it will now be evident that a motor-pumpunit constructed in accordance with the principles of the presentinvention provides a simplified and compact arrangement withoutsacrificing motor or pump performance. By mounting the pump directly onthe stator and using the stator core as the supporting frame for themotor and pump unit, there is no longer any need for the usual cuporbell-shaped casting hitherto used in hermetic compressors to form theinboard bearing bracket and to mount and center the motor shaft inrelation to the stator. Such bell-shaped bearing brackets of prior artcompressors are relatively large and heavy cast parts which necessitateda rather large structural height (in vertical shaft pumps orcompressors) or axial dimension because the compressor or pump alongwith its associated drive means have to be mounted on the side of thebearing bracket remote from the electric motor. By doing away with thisheavy and costly part, the present invention significantly reduces theweight and cost of the total unit. In addition, the exterior dimensionsare considerably reduced because the cylinder block is nested directlyagainst the stator in the space provided by opening up the gap in theend turns of the stator windings of the motor.

The arched configuration of the combined bearing bracket 140 and boss138 further contributes to the axial compactness of the unit and permitsthe use of a rotor 148 of conventional cast aluminum construction.Although stator core 36 has a unique winding slot arrangement, itnevertheless does not depart so far from conventional stator design asto preclude use of existing automatic motor winding machinery andexisting stator manufacturing equipment to manufacture stator core 36.The bonding of the stator laminations to one another by an epoxyadhesive adds little to the cost of stator construction but greatlyincreases its strength so that it can serve as the primary structuralsupport for the motor-compressor unit 30.

It is to be understood that the principles of the present invention canbe applied to other types of electric motors, such as split phaseinduction motors, capacitor start-capacitor run induction motors(two-value capacitor induction motors) and permanent split capacitorinduction motors. For example, such single phase induction motors may bebuilt as two-pole motors as described previously herein or may be afour-pole type having a stator made up of two main or run windings whichare placed at right angles to each other around the stator. Thismodification uses a distributed multiple coil arrangement wherein thecoils forming one-half of one of the main windings is arranged in astator core constructed similarly to core 36 in a manner similar tocoils 98-104. The remaining three sets of winding coils likewise areinterrelated following the relationship of coils 90-96, 110-116 and122-128. In addition, suitable resistance or capacitance start circuitrymay be employed to alter the phase angle relationship between thewindings to partially or wholly compensate for any angular physicaldisplacement of the coils from the usual 90 spacing. In either instancethe windings are preferably reoriented only insofar as it is necessaryto open up a single mounting portion 82 on the stator core. Hence, thearrangement of the invention permits the use of a maximum number offield windings withing the space available so as to retainhigh-operating efficiency while achieving a minimum dimension package.

It is also to be understood that the invention is not limited to theparticular 20-slot stator 36 described by way of example herein, but mayalso be applied to stators having, for example, 18 or 22 slots. Also,successful results have been obtained with slots of uniform radialdimension as shown in FIG. 6 as well as with a modification thereofwherein slots 60 and 62 are slightly shorter in radial dimension thanthe remaining slots of the stator. Although the illustrative example ofthe motor described previously herein employs four coils per pole in thestarting winding, it is possible to vary this and to use, for example,three or five coils per pole. The stator cores 36 of the motors employedin accordance with the invention may have their laminations securedtogether only by adhesive bonding as described previously herein withreference to stator 36, or the stator may be both core bonded andwelded, or core bonded and cleated.

FIGS. 11-16 inclusive illustrate a modified motor-compressor unit 20' ofthe present invention which is similar to unit 20 but modified withrespect to the bearing support structure and associated rotor shaft-pumpcrankshaft. In FIGS. 1 1-16 inclusive those parts corresponding to theparts described previously in connection with the motor-compressor 20are given like reference numerals and their description not repeatedherein. The modified unit 20 employs a unibearing support for the rotorshaft-crankshaft 300 wherein a single bearing hub 302, east integrallywith a modified cylinder block 304, is cantilevered from the block tosupport shaft 300 and in turn rotor 306. Block 304 is mounted in thesame manner as block 136 and is preferably constructed of S.A.E. 308aluminum alloy. A cylinder liner 308 made of cast iron is cast into theblock and defines the cylinder bore 310 of the compressor pump.

By way of further explanation, block 304 has a boss 353 (FIG. 13) havinga threaded counterbore 354 to receive one end of a compressor dischargetube. Block 304 also has an internal passageway 356 communicating withcounterbore 354 at one end and with the discharge chamber 212 at theopposite end of the block. It is also to be understood that the flatupper surface 358 of block 304 is adapted to receive a coverplate (notshown) with suitable gasketing, and is secured to the box by suitablestuds to close the chamber 221 described previously.

A mounting boss portion 312 of block 304 is, like the corresponding boss138 of block 136, seated flat on the upper surface of core 36 in the gapof the upper end turn ring 132 and bearing hub 302 projects radiallyinwardly to the center of the stator, similar to the inboard bearing hub140 described previously.

However, instead of the crankshaft being joumaled directly in hub 302,the same is provided with a main journal insert 314 (shown by itself inFIGS. 14, 15 and 16). Journal insert 314 is preferably made ofcold-rolled steel and provided with external screw threads 316 adjacentits upper end which are threadably received within the internallythreaded bore 318 of hub 302. Insert 314 has an external flange 320adapted to seat against the underside of hub 302.

As best seen in FIGS. 15 and 16, journal insert 314 is preferablyprovided with flats 321 and 321' in the lower comer of flange 320 anddiametrically opposite one another to provide a convenient means forapplying a wrench to screw the journal into hub 302. Both the lowercomer of hub 302 and the outer surface of flange 320 are tapered toprovide a clearance space between these tapered surfaces and thecomplimentary tapered inner surface of the upper end ring 322 of rotor306. Insert 314 has a reduced diameter shank portion 324 extendingdownwardly from flange 320 to the lower free end of the insert which isadapted to nest with the clearance within a counterbore 326 in a coresleeve 328 of rotor 306. Sleeve 328 is supported on a shank portion 330of shaft 300 with a press fit to secure the shaft for rotation with therotor, the upper half of shank 330 being joumaled for rotation withinthe bore 332 of insert 314. An axial thrust bearing to support theweight of the upright shaft 300 and rotor 306 is formed by the machinedupper end surface 334 of journal 314 and the machined undersurface of anenlarged diameter head portion 336 of shaft 300.

Preferably a stepped cylindrical dip tube 338 as disclosed in U.S. Pat.No. 3,410,478 is secured to the lower end of shaft 300 to centrifugallypump oil up the hollow bore 340 of shaft 300 to a radially offsetaxially extending passage 342 in crankpin 172. Lubricating and coolingoil thus is pumped up to and slung from the upper end of crankshaft forlubrication of the shaft unibearing as well as the reciprocating piston168 of the compressor pump. The upper rim 348 of insert 314 is providedwith a slot 350 as shown FIG. 14 extending at an angle to a radius ofthe insert. Slot 350 is oriented to serve as an oil scraper for drawingoil into the annular space 351 between an undercut in shaft 330 andbearing bore 332 in response to counterclockwise rotation of shaft 300.The oil collecting on the upper surface 352 of hub 302 tends to drain.to slot 350 and thus serves as a source of supply for oiling the upperend surface 334 as well as the bore 332 of insert 314.

With the above-described unibearing modification, the need for thepreviously described outboard bearing bracket 150 is eliminated. Inaddition, the relatively long axial dimension of the main journal insert314 reduces the inboard bearing load and thus provides improvedantifriction characteristics for this reason and due to the oil beingfed into the upper end of bearing bore 332 via slot 350. Moreover,lubricating oil is also collected by the funnel-shaped clearance betweenend ring 322 and hub 302-flange 320, from which the oil drains into thelower end of the bearing bore 332 via the clearance space between shank324 and counterbore 326. This clearance space is closed at its lower endby the shoulder 329 of the rotor sleeve 328. Hence these clearancespaces form an oil sump for feeding oil directly to shank 330, and thepressure head as well as capillary action forces the oil up into bore332 of journal 314. Shoulder 329 also serves as a stop to limit axiallyupward movement of shaft 300 in the journal 314.

This unibearing design is advantageous. in that the main journal insertmay be precision machined and made of stronger, more wear resistantmaterials such as cold-rolled steel. Since the insert 314 is disposedcentrally of the stator and is insulated magnetically from the stator bythe aluminum material of block 304, it exerts a minimum magneticinfluence on the core 36. All of the above factors contribute to longerbearing life and reduced starting resistance in the pump drive.

It is also to be understood that the above-described unibearing designmay be constructed in one piece similar to the construction of theinboard bearing 140 of the previously described embodiment. In such amodification, the main journal is formed integrally with the bearing hub302. In order to assemble the piston rod 176 to the crankshaft 300 insuch modification, the rod is split at the big end thereof in accordancewith conventional practice so that assembly of the piston rod can followassembly of the crankshaft in the integral unibearing.

lclaim:

1. In a hermetic compressor the improvement comprising an electricinduction motor having a stator and a rotor, first and second runwindings wound on said stator and disposed to form electrical fieldpoles generally opposite one another diametrically of saidrotor, saidrun windings having end turns projecting beyond both of the axiallyopposite ends of said stator, said end turns of said first and secondwindings being arranged in a horseshoe configuration at each of saidends of said stator so as to extend circumferentially of said statoradjacent one another and such that the end turns of both said first andsecond windings traverse one of said field poles and respectively definefirst and second gaps therein each exposing a portion of the adjacentsurface of the associated end of said stator, said gaps being located inthe vicinity of the other of said field poles, a piston-type compressormounted on at least one of said exposed surface portions of said statorso as to be nested in the associated one of said gaps, means support ingsaid rotor for rotation in said stator, and means drivingly connectingsaid rotor to the piston of said compressor.

2. In the compressor as set forth in claim 1 the further improvementwherein said compressor has a cylinder block constructed of nonmagneticmaterial, said block being secured to said stator in the portion thereofaxially between said gaps to support said compressor on said stator.

3. In the compressor as set forth in claim 2 the further improvementwherein said cylinder block has an inboard bearing bracket castintegrally therewith to form part of said rotor sup port means, thesides of said cylinder block and said inboard bearing bracket facingsaid stator having an annular notch therein, and wherein said rotor hasan axial projection at the end thereof adjacent said block disposed forrotation through said annular notch.

4. In the compressor as set forth in claim 2 the furtherimprovementwherein said rotor support means comprises an outboard bearing bracketmade of nonmagnetic material and disposed in said second gap on the sideof said stator opposite said cylinder block, and said outboardbearingbracket and cylinder block are clamped to said stator byfastening means extending axially through said stator to connectionswith said outboard bearing bracket and said block.

5. In the compressor as set forth in claim 1 the further improvementwherein said stator comprises a plurality of laminations of magneticmaterial secured to one another by an adhesrve.

6. In the compressor as set forth in claim 1 the further improvementwherein said compressor is secured to said stator in said first 'gap bya plurality of fastener means disposed in said second gap and extendingaxially through said stator to connections with said compressor tothereby clamp said compressor against said one exposed surface portion,and means electrically insulating said fastener means from said statorand insulating said fastener means from one another at the ends of saidfastener means located in said second gap.

7. In a hermetic compressor, the combination comprising a single phasealternating current induction motor having a stator and a rotor, firstand second run windings and first and second start windings wound onsaid stator and having end turns projecting beyond the axially oppositeends of said stator, said end turns of said first run winding extendingcircumferentially of said stator adjacent the end turns of said secondrun winding, said end turns of all of said windings forming a horseshoeconfiguration at each of said ends of said stator defining first andsecond axially aligned gaps in said windings, each of said gaps exposinga portion of adjacent surface of the associated end of said stator, apiston-type compressor mounted on at least one of said exposed surfaceportions of said stator, and means drivingly connecting said rotor tothe piston of said compressor, said run winding being arranged on acommon axis extending diametrically of said rotor, said start windingsbeing disposed generally opposite one another diametrically of saidrotor and laterally of said common axis of said run windings and offsettoward the portion of said stator diametrically opposite said gaps.

8. In the compressor as set forth in claim 7 the further improvementwherein said stator has a circular row of axially and radially extendingwinding slots arranged in a circular row therearound through acircumferential extent of approximately 300 with the ends of said rowterminating on opposite sides of said gaps, said windings eachcomprising a plurality of coils each distributed in pairs of said slots.

9. In the compressor as set forth in claim 8 the further improvementwherein said plurality of slots consist of 20 slots numbered herein foridentification consecutively one through 20 and spaced at equal angularintervals around said stator adjacent the inner periphery thereof withslots numbers one and 20 bounding said gaps, and wherein each of saidwindings consists of four coils, said four coils of said first runwinding being wound through said slots numbered one through four and 17through 20 and with the two runs of each coil of. said first run windingdisposed opposite one another on a line perpendicular to said commonaxis, said four coils of said second run winding being wound in likemanner through said slots numbered five through eight and 13 through l6,said four coils of said first start winding being wound through slotsone through four and seven through 10 and'said four coils of said secondstart winding being wound through slots 1 1 through 14 and 17 through20.

10. In an electric motor and pump unit having-a stator with an annularcore having a plurality of winding slots disposed in a circular rowaround the inner periphery of said core, the improvement wherein saidstator core has an unslotted portion disposed between the ends of saidrow of slots, a series of field windings wound through said slots andhaving end turns projecting beyond each of the axially opposite endsurfaces of said core, said end turns being arranged in a horseshoeconfiguration whereby'a gap is formed in each of said end turns exposinga portion of each of said end'surfaces axially aligned with saidunslotted portion of said core, a pump unit mounted on said statorincluding a cylinder block secured to said unslotted portion of saidcore and disposed with its cylinder axis perpendicular to the axis ofsaid stator, bearing means secured to the unslotted portion of said coreand extending radially inwardly therefrom, .a rotor shaft journaled insaid bearing means coaxial with said stator and carrying a rotorthereon, and means forming a driving connection between said rotor and apiston received in said cylinder for imparting reciprocation to saidpiston in response to rotation of said rotor.

11. The motor-pump unit as set forth in claim wherein said cylinderblock and bearing means are constructed of nonmagnetic material.

12. The motor-pump unit as set forth in claim 11 wherein said statorcore comprises a plurality of laminations of magnetic material securedto one another by an adhesive.

13. The motor-pump unit as set forth in claim 11 wherein said cylinderblock has an inboard bearing bracket cast integrally therewith to format least part of said bearing means, the side of said cylinder block andsaid inboard bearing bracket facing said core having an arcuate notchformed therein, and wherein said rotor has an axial projection at theend thereof adjacent said block disposed for rotation through saidarcuate notch.

14. The motor-pump unit as set forth in claim 11 wherein said bearingmeans comprises an outboard bearing bracket disposed on the side of saidcore opposite said cylinder block and said outboard bearing bracket andcylinder block are clamped to said core by fastening means extendingaxially through said core to connections with said outboard bearingbracket and said cylinder block.

15. The motor-pump unit as set forth in claim 10 wherein said fasteningmeans comprises a plurality of steel fasteners extending axially throughsaid unslotted portion of said core, each fastener having at one end athreaded connection to said cylinder block and at the other end thereofa clamping connection with said core, and means electrically insulatingsaid fasteners from said core and from one another at said other endsthereof.

16. In a hermetic compressor having a hermetic casing with analternating current single phase electric motor and pump unitresiliently supported therein, the improvement comprising an annularlaminated stator core having a plurality of winding slots disposed in acircular row around the inner periphery of the stator, said stator corehaving an unslotted portion disposed between the ends of said row ofslots, a pair of run windings and a pair of start windings wound in adistributed manner through said slots, said windings having end turnsprojecting beyond the axially opposite end surfaces of said core andtogether forming a horseshoe configuration at each of the axiallyopposed ends of said core to thereby define axially aligned gaps in saidend turns registering with said unslotted portion of said core, saidpump unit including a cylinder block secured to said unslotted portionof said core and disposed with its cylinder axis perpendicular to theaxis of said stator, inboard and outboard bearing means mountedrespectively to the axially opposite surfaces of said unslotted portionof said stator and extending radially inwardly therefrom, a rotor shaftjournaled in said bearing means coaxial with said stator and carrying arotor therein, and means forming a driving connection between said rotorand a piston received in said cylinder for imparting reciprocation tosaid piston in response to rotation of said rotor.

17. In a hennetic compressor having a hermetic casing with an electricmotor and pump unit supported therein, the improvement comprising astator core having an unslotted portion disposed between windings woundon said core and having first end turns projecting beyond one end ofsaid core and second end turns projecting beyond the axially oppositeend of said core, said end turns being arranged to define first andsecond gaps in said first and second end turns respectively,

said gaps registering with said unslotted portion of said core, saidpump unit including a cylinder block secured to said unslotted ortion ofsaid core at said one end thereof and dispose with its cylinder axisperpendicular to the axis of said stator, inboard bearing meanscantilever connected to said block and extending radially inwardly fromsaid cylinder block and terminating short of the portion of the innerperiphery of said core radially opposite said unslotted portion, a rotorshaft journaled in said bearing means coaxial with said stator andcarrying a rotor thereon and means forming a driving connection betweensaid rotor and a piston received in said cylinder for impartingreciprocation to said piston in response to rotation of said rotor.

18. The compressor as set forth in claim 17 wherein said inboard bearingmeans comprises a hub having a bore concentric with said rotor shaft anda main journal insert secured in said hub bore and coaxially dependenttherefrom, said insert having a bore in which said rotor shaft isjournaled.

19. The compressor as set forth in claim 18 wherein said insert has asleeve extending axially from said hub and terminating between said endsof said core, said rotor having a sleeve secured to said rotor shaftbetween said sleeve of said insert and said opposite end of said core,said rotor axially overlapping and encircling said sleeve of said insertand defining therewith an annular cavity for collecting lubricant andsupplying the same to said rotor shaft between said insert sleeve andsaid rotor sleeve.

20. The compressor as set forth in claim 19 wherein said main journalinsert has a radially projecting external flange adapted to abut saidhub on the side thereof facing said rotor, and said hub bore and saidinsert have mating threads whereby said insert may be screwed into saidbore to bring said flange into abutment with said hub.

21. The compressor as set forth in claim 20 wherein said insert has abearing surface at the end thereof opposite said sleeve of said insertand disposed in a plane perpendicular to the axis of said rotor shaft,and said rotor shaft has a head radially overlapping said end bearingsurface of said insert, said head having a bearing surface seating onsaid insert bearing surface to form an axial thrust bearing for saidrotor shaft.

22. The compressor as set forth in claim 21 wherein said one end of saidinsert has a slot extending between the bore of said insert and theexterior of said insert, said slot being covered by said head of saidrotor shaft and serving to feed oil to said insert bore, said hub havinga surface encircling said insert generally flush with said slot to feedoil to said slot.

23. The compressor as set forth in claim 18 wherein said block and hubare cast integrally as a unit from a structural aluminum alloy and saidinsert is made of steel.

24. The compressor as set forth in claim 17 further including anoutboard bearing means cantilever connected to said unslotted portion ofsaid core at said opposite end thereof and extending radially inwardlytherefrom, said outboard bearing means having a hub portion coaxial withsaid rotor shaft and spaced axially from said inboard means, said rotorshaft being journaled in said inboard and outboard bearing means, saidrotor being secured to said rotor shaft intermediate said inboard andoutboard bearing means. e

25. The compressor as set forth in claim 24 wherein said cylinder blockand said outboard bearing means are clamped to said unslotted portion ofsaid core by fastener means extending axially through said unslottedportion of said stator core and having connections with said block andsaid outboard bearing means.

26. The compressor as set forth in claim 25 wherein said fastener meanscomprise a plurality of steel studs each threaded at one end into saidcylinder block, and including means electrically insulating said studsfrom said core and from said outboard bearing means.

1. In a hermetic compressor the improvement comprising an electricinduction motor having a stator and a rotor, first and second runwindings wound on said stator and disposed to form electrical fieldpoles generally opposite one another diametrically of said rotor, saidrun windings having end turns projecting beyond both of the axiallyopposite ends of said stator, said end turns of said first and secondwindings being arranged in a horseshoe configuration at each of saidends of said stator so as to extend circumferentially of said statoradjacent one another and such that the end turns of both said first andsecond windings traverse one of said field poles and respectively definefirst and second gaps therein each exposing a portion of the adjacentsurface of the associated end of said stator, said gaps being located inthe vicinity of the other of said field poles, a piston-type compressormounted on at least one of said exposed surface portions of said statorso as to be nested in the associated one of said gaps, means supportingsaid rotor for rotation in said stator, and means drivingly connectingsaid rotor to the piston of said compressor.
 2. In the compressor as setforth in claim 1 the further improvement wherein said compressor has acylinder block constructed of nonmagnetic material, said block beingsecured to said stator in the portion thereof axially between said gapsto support said compressor on said stator.
 3. In the compressor as setforth in claim 2 the further improvement wherein said cylinder block hasan inboard bearing bracket cast integrally therewith to form part ofsaid rotor support means, the sides of said cylinder block and saidinboard bearing bracket facing said stator having an annular notchtherein, and wherein sAid rotor has an axial projection at the endthereof adjacent said block disposed for rotation through said annularnotch.
 4. In the compressor as set forth in claim 2 the furtherimprovement wherein said rotor support means comprises an outboardbearing bracket made of nonmagnetic material and disposed in said secondgap on the side of said stator opposite said cylinder block, and saidoutboard bearing bracket and cylinder block are clamped to said statorby fastening means extending axially through said stator to connectionswith said outboard bearing bracket and said block.
 5. In the compressoras set forth in claim 1 the further improvement wherein said statorcomprises a plurality of laminations of magnetic material secured to oneanother by an adhesive.
 6. In the compressor as set forth in claim 1 thefurther improvement wherein said compressor is secured to said stator insaid first gap by a plurality of fastener means disposed in said secondgap and extending axially through said stator to connections with saidcompressor to thereby clamp said compressor against said one exposedsurface portion, and means electrically insulating said fastener meansfrom said stator and insulating said fastener means from one another atthe ends of said fastener means located in said second gap.
 7. In ahermetic compressor, the combination comprising a single phasealternating current induction motor having a stator and a rotor, firstand second run windings and first and second start windings wound onsaid stator and having end turns projecting beyond the axially oppositeends of said stator, said end turns of said first run winding extendingcircumferentially of said stator adjacent the end turns of said secondrun winding, said end turns of all of said windings forming a horseshoeconfiguration at each of said ends of said stator defining first andsecond axially aligned gaps in said windings, each of said gaps exposinga portion of adjacent surface of the associated end of said stator, apiston-type compressor mounted on at least one of said exposed surfaceportions of said stator, and means drivingly connecting said rotor tothe piston of said compressor, said run winding being arranged on acommon axis extending diametrically of said rotor, said start windingsbeing disposed generally opposite one another diametrically of saidrotor and laterally of said common axis of said run windings and offsettoward the portion of said stator diametrically opposite said gaps. 8.In the compressor as set forth in claim 7 the further improvementwherein said stator has a circular row of axially and radially extendingwinding slots arranged in a circular row therearound through acircumferential extent of approximately 300* with the ends of said rowterminating on opposite sides of said gaps, said windings eachcomprising a plurality of coils each distributed in pairs of said slots.9. In the compressor as set forth in claim 8 the further improvementwherein said plurality of slots consist of 20 slots numbered herein foridentification consecutively one through 20 and spaced at equal angularintervals around said stator adjacent the inner periphery thereof withslots numbers one and 20 bounding said gaps, and wherein each of saidwindings consists of four coils, said four coils of said first runwinding being wound through said slots numbered one through four and 17through 20 and with the two runs of each coil of said first run windingdisposed opposite one another on a line perpendicular to said commonaxis, said four coils of said second run winding being wound in likemanner through said slots numbered five through eight and 13 through 16,said four coils of said first start winding being wound through slotsone through four and seven through 10 and said four coils of said secondstart winding being wound through slots 11 through 14 and 17 through 20.10. In an electric motor and pump unIt having a stator with an annularcore having a plurality of winding slots disposed in a circular rowaround the inner periphery of said core, the improvement wherein saidstator core has an unslotted portion disposed between the ends of saidrow of slots, a series of field windings wound through said slots andhaving end turns projecting beyond each of the axially opposite endsurfaces of said core, said end turns being arranged in a horseshoeconfiguration whereby a gap is formed in each of said end turns exposinga portion of each of said end surfaces axially aligned with saidunslotted portion of said core, a pump unit mounted on said statorincluding a cylinder block secured to said unslotted portion of saidcore and disposed with its cylinder axis perpendicular to the axis ofsaid stator, bearing means secured to the unslotted portion of said coreand extending radially inwardly therefrom, a rotor shaft journaled insaid bearing means coaxial with said stator and carrying a rotorthereon, and means forming a driving connection between said rotor and apiston received in said cylinder for imparting reciprocation to saidpiston in response to rotation of said rotor.
 11. The motor-pump unit asset forth in claim 10 wherein said cylinder block and bearing means areconstructed of nonmagnetic material.
 12. The motor-pump unit as setforth in claim 11 wherein said stator core comprises a plurality oflaminations of magnetic material secured to one another by an adhesive.13. The motor-pump unit as set forth in claim 11 wherein said cylinderblock has an inboard bearing bracket cast integrally therewith to format least part of said bearing means, the side of said cylinder block andsaid inboard bearing bracket facing said core having an arcuate notchformed therein, and wherein said rotor has an axial projection at theend thereof adjacent said block disposed for rotation through saidarcuate notch.
 14. The motor-pump unit as set forth in claim 11 whereinsaid bearing means comprises an outboard bearing bracket disposed on theside of said core opposite said cylinder block and said outboard bearingbracket and cylinder block are clamped to said core by fastening meansextending axially through said core to connections with said outboardbearing bracket and said cylinder block.
 15. The motor-pump unit as setforth in claim 10 wherein said fastening means comprises a plurality ofsteel fasteners extending axially through said unslotted portion of saidcore, each fastener having at one end a threaded connection to saidcylinder block and at the other end thereof a clamping connection withsaid core, and means electrically insulating said fasteners from saidcore and from one another at said other ends thereof.
 16. In a hermeticcompressor having a hermetic casing with an alternating current singlephase electric motor and pump unit resiliently supported therein, theimprovement comprising an annular laminated stator core having aplurality of winding slots disposed in a circular row around the innerperiphery of the stator, said stator core having an unslotted portiondisposed between the ends of said row of slots, a pair of run windingsand a pair of start windings wound in a distributed manner through saidslots, said windings having end turns projecting beyond the axiallyopposite end surfaces of said core and together forming a horseshoeconfiguration at each of the axially opposed ends of said core tothereby define axially aligned gaps in said end turns registering withsaid unslotted portion of said core, said pump unit including a cylinderblock secured to said unslotted portion of said core and disposed withits cylinder axis perpendicular to the axis of said stator, inboard andoutboard bearing means mounted respectively to the axially oppositesurfaces of said unslotted portion of said stator and extending radiallyinwardly therefrom, a rotor shaft journaled in said bearing meanscoaxial with said stator and carrying a rotor therein, and means forminga dRiving connection between said rotor and a piston received in saidcylinder for imparting reciprocation to said piston in response torotation of said rotor.
 17. In a hermetic compressor having a hermeticcasing with an electric motor and pump unit supported therein, theimprovement comprising a stator core having an unslotted portiondisposed between windings wound on said core and having first end turnsprojecting beyond one end of said core and second end turns projectingbeyond the axially opposite end of said core, said end turns beingarranged to define first and second gaps in said first and second endturns respectively, said gaps registering with said unslotted portion ofsaid core, said pump unit including a cylinder block secured to saidunslotted portion of said core at said one end thereof and disposed withits cylinder axis perpendicular to the axis of said stator, inboardbearing means cantilever connected to said block and extending radiallyinwardly from said cylinder block and terminating short of the portionof the inner periphery of said core radially opposite said unslottedportion, a rotor shaft journaled in said bearing means coaxial with saidstator and carrying a rotor thereon and means forming a drivingconnection between said rotor and a piston received in said cylinder forimparting reciprocation to said piston in response to rotation of saidrotor.
 18. The compressor as set forth in claim 17 wherein said inboardbearing means comprises a hub having a bore concentric with said rotorshaft and a main journal insert secured in said hub bore and coaxiallydependent therefrom, said insert having a bore in which said rotor shaftis journaled.
 19. The compressor as set forth in claim 18 wherein saidinsert has a sleeve extending axially from said hub and terminatingbetween said ends of said core, said rotor having a sleeve secured tosaid rotor shaft between said sleeve of said insert and said oppositeend of said core, said rotor axially overlapping and encircling saidsleeve of said insert and defining therewith an annular cavity forcollecting lubricant and supplying the same to said rotor shaft betweensaid insert sleeve and said rotor sleeve.
 20. The compressor as setforth in claim 19 wherein said main journal insert has a radiallyprojecting external flange adapted to abut said hub on the side thereoffacing said rotor, and said hub bore and said insert have mating threadswhereby said insert may be screwed into said bore to bring said flangeinto abutment with said hub.
 21. The compressor as set forth in claim 20wherein said insert has a bearing surface at the end thereof oppositesaid sleeve of said insert and disposed in a plane perpendicular to theaxis of said rotor shaft, and said rotor shaft has a head radiallyoverlapping said end bearing surface of said insert, said head having abearing surface seating on said insert bearing surface to form an axialthrust bearing for said rotor shaft.
 22. The compressor as set forth inclaim 21 wherein said one end of said insert has a slot extendingbetween the bore of said insert and the exterior of said insert, saidslot being covered by said head of said rotor shaft and serving to feedoil to said insert bore, said hub having a surface encircling saidinsert generally flush with said slot to feed oil to said slot.
 23. Thecompressor as set forth in claim 18 wherein said block and hub are castintegrally as a unit from a structural aluminum alloy and said insert ismade of steel.
 24. The compressor as set forth in claim 17 furtherincluding an outboard bearing means cantilever connected to saidunslotted portion of said core at said opposite end thereof andextending radially inwardly therefrom, said outboard bearing meanshaving a hub portion coaxial with said rotor shaft and spaced axiallyfrom said inboard means, said rotor shaft being journaled in saidinboard and outboard bearing means, said rotor being secured to saidrotor shaft intermediate said inboard and outboard bearing means. 25.The compressor as set forth in claim 24 wherein said cylinder block andsaid outboard bearing means are clamped to said unslotted portion ofsaid core by fastener means extending axially through said unslottedportion of said stator core and having connections with said block andsaid outboard bearing means.
 26. The compressor as set forth in claim 25wherein said fastener means comprise a plurality of steel studs eachthreaded at one end into said cylinder block, and including meanselectrically insulating said studs from said core and from said outboardbearing means.